Manufacture of lubricants



Patented Jan. 20, 1942 2,270,620 MANUFACTURE or LUBRICANTS Ulric B. Bray, Palos Verdes Estates? Calif., as-

signor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application August 2, 1937,

Serial No. 156,960

'18 Claims.

This invention relates to modified lubricants particularly mineral lubricating oils, but may also be extended to greases, where such lubricants contain soaps as modifiers of the lubricating oil.

The primary object of this invention is to produce stable lubricating oils containing additives to impart oiliness and stabilizing characteristics, which modified oils shall be resistant to extreme pressure conditions and capable of avoiding deposits of soot, gum, resins and varnish-like materials upon and about the valves and rings of internal combustion engines and of preventing the sticking of rings and valves, especially in engines of the Diesel type. It is a further object to so stabilize such soap suspensions in oil that separation of the soap under severe service condior otherwise halogenated by bubbling chlorine gas through the acids at slightly'elev'ated temperatures to maintain fluidity, in either the prestions, for example under the influence of internal combustion engine heat, will not occur. This application is a continuation in part of my copending application Serial No. 121,167, filed January 18,1937, now issued as' Patent No. 225,365 of December 17, 1940, and the objects to be attained there and the conditions to be avoided are also sought by reason of the present disclosure.

Statement of invention Primarily the invention resides in the employment of oil-soluble soaps of the alkaline earth metals, and particularly applies to calcium soaps,

of the halogenated and unhalogenated synthetic petroleum acids produced by oxidation of normally liquid highly refined, highly paraflinic petroleum lubricating oils, which soaps are oil-solubig and have fairly high molecular weights, containing in excess of ten carbon atoms. .With certain of the synthetic petroleum acids, the soaps of other metals, such as magnesium, aluminum, lead and zinc are sufiiciently soluble in lubricating oil to be used.

These liquid petroleum lubricating fractions, both light and heavy, may be oxidized according to known practices with the resultant production of complex petroleum acids. It would appear that the synthetic oxidation acids obtained from highly refined heavily solvent-treated lubricating sure oil solubility of the metal soaps produced therefrom. These synthetic petroleum acids can be separated according to known practices as complex mixtures but relatively free from undesirable impurities produced also during the oxidation and from unoxidized hydrocarbons. These synthetic j ectionable materials.

ence or absence of a halogenation catalyst such as phosphorus or phosphorous chloride.

Having obtained such ,synthetic petroleum'd' acids, the desired soaps.may be produced in either of two ways", According to one procedure the acids are reacted vvith a suitable alkaline earth metal compound (preferably calcium or magnesium) with resultant formation of the soap, which soap is thenadded to lubricating oil. Again the acids maybe added directly to the lubricating oil fraction to he modified and small amounts of such alkaline earth metal materials as calcium oxide or hydroxide or magnesium oxide or hydroxide added to the mixture. In this fashion the soaps are formed in the oil and undesired by-products may beremoved by heating and filtering. If desired-,a small quantity of clay may be added to the treatment to facilitate separation. In practice, as an example 1% or 1.5% of any suitable. petroleum acid produced by oxidation as above indicatedni ay be added to the oil and about-0.2% of calcium oxide or h droxide introduced and the mixture is heated to 325 F. with agitation after the evolution of moisture is complete the mixtureis filtered. After filtration, the oil contains the desired amount of soap. Also, the oxidation of the oil may take place in the presence of'the alkalineearth compound so that the soaps are formed as rapidly as the acid products are formed. Filtration or removal during subsequent clay treatment, may be relied upon to remove all suspended and ob- Such a soap-containing oil has been found to be highly satisfactory for use in internal combustion engines, particularly the Diesel engine type, for overcoming ring sticking, varnish formation and deposition of soot, gums, resins and the like.

In order to insure tipn of the soapand to maintain the desired dispersion of the soap in the oil, I have some;

times found it desirable to add a small fraction,

for example 0.05% to 0.2% of a. stabilizing material of the character of triethanolamine, or other basic, organic, preferably .aliphatic amine which is non-volatile at crankcase temperatures.

Whether this material functions in its original form or whether it combines with excess acids re-' maining after saponification, or with acids which against occasional separai tend to develop during use or whether triethanolpetroleum acids may or may-not be chlorinated amine is present both assuch andin the form of some of its soaps, is not clear. However, the soaps of the synthetic petroleum acids considered under the present invention usually do not require an added stabilizer.

Ordinarily the soaps of synthetic petroleum acids are employedin any ordinary grade of min eral lubricating oil for example S. A. E. 30 in amounts between about 1% and 2%. But this concentration of soaps can be varied according to the lubricating stock, the use intended, and other factors, so that an over-all range may be between about 0.6% or 0.8% and 2% or 3%. It-is possible in many instances to increase the upper limit to perhaps 3% or even beyond for purposes of engine lubricating oil, by adding triethanolamine or its soaps for the reason that triethanolamine or a soap thereof largely overcomes any tendency toward viscosity increase by reason of the addition of the synthetic petroleum acid soaps.

As a suitable lubricating oil, it is preferred ordinarily to employ an oil which in itself offers minimum formation of gums, resins, varnishes and the like, such as a naphthenic base oil, but the invention is not necessarily limited to stocks which are essentially naphthenic in character,

and sometimes may be applied to other oils including the more niodern highly refined or highly paraiiinic oils such as ordinary grade Pennsylvania oils or solventextracted oils.

While the invention is intended to apply primarily to engine lubricating oils and the like, it is not limited thereto and may be extended to greases, both the normally fluid and normally solid type, by increasing the percentage of the petroleum acid soaps both with and without the use of triethanolamine. Where thelatter is used it is employed in such quantity as stabilizes the grease and insures against separation. Inasmuch as such greases are normally employed at ordinary temperatures, the amount of triethanolamine required will be. comparatively small with respect to the content of petroleum acid soaps, for example around 0.1 or 0.2%.

To stabilize against water-sensitiveness, instead of adding triethanolamine to an oil containing calcium or magnesium soap, I may add a small percentage of water, for example 1% to 3%, and boil the soapy oil. As'argsult those portions of the soap which are sensitive to the presence of water are precipitated in the froth which results and may be removed therein. Not only does this boiling or frothing operation tend to stabilize the oil composition but it also renders the oil resistant to the presence of small portions of water which may be encountered in use. When only about 1% of water is employed for this purpose only a portion of the water-sensitive soaps are removed, but when 3% is employed the greater proportion of such soaps is eliminated.

The invention therefore further includes the 7 addition of the above described soapsof oxidation products to lubricating oils, particularly to naphthenic-base oils as severe service oils such as Diesel engines lubricating oil, and also for acids, which acids and their salts especially the calcium and magnesium salts are highly soluble in lubricating oil fractions and. are retained therein without difliculty.

Such olls are'produced by-the more modern heavy solvent refining of dewaxed oils such as mixed or parafiinic base oils, as eleswhere herein mentioned. Solvents well-known for this purpose include liquid sulphur dioxide-benzene mixtures, furfural, dichlorethylether, phenol, cresol,

nitrobenzene and others used alone or in the presence of propane. This heavy solvent refining removes the aromatic and more reactive constituents, but leaves along with the highly paraflinic materials a quantity of highly stable naphthenic orring containingmaterials with long paraiiin side chains which are good oxygen receptors. At any rate I postulate the existence of such materials and the probability that a large proportion of valuble lubricating constituents which have heretofore been accepted as highly paraflinic long chain hydrocarbons are in fact largely composed of five and six membered rings protected by long paraflinic chains.

a kindred chemical treatment.

protected aromatic or ring compounds. There' is then left as the main lubricating constituent a stable paraflinic type material. These lubricating oil fractions which produce satisfactory acids and their soaps have an API gravity between 22 and 35 at F. Heretofore-it has ordinarily been assumed that these materials are highly paraflinic in character, that is of the straight chain or aliphatic type. However, I have found much evidence to convince me that these highly valuable lubricating materials are in fact at least in large part ring compounds heavily protected with paraflinic side chains, and the long-chain protection of the rings prevents the materials,

from being removed by solvent extraction or The result is a highly stable material which can be oxidized to build up a substantial oxidation content without the production of sludges. This last characteristic of avoidance of sludges is perhaps the important aspect of the so-called highly parafllnic to the various combinations and other features of novelty herein disclosed.

Oxidation I have found that certain highly refined lubricating fractions which contain some naphthenic or other ring structures may be oxidized to yield mineral lubricating fractions of the mentioned types of lubricating oils.

Inaddition to these paramnic materials, which I postulate to be rings heavily protected with long side chains and which possessalow viscosity gravity constant (V. G. C.) in the order of 0.840 to 0.785, I may also use oils of a higher 'viscosity'gravity constant such as Edeleanu treated or acid treated lubricating oils obtained from naphthenic stocks such as those frequently referred to as Western or Gulf Coastal stocks. Oils of this type may have viscosity gravity constants in the order of 0.840 to 0.885. such oils in turn have their aromatic and unprotected ring compounds large-- instances where materials are desired that have in themselves solvent properties for gums, resins, varnishes or similar ring sticking constituents. The Edeleanu process mentioned is the wellknown treatment with liquid sulphur dioxide which removes the more reactive and aromatic constituents. In the case of oxidation of materials of this type any objectional oil-insoluble products resulting will of course be removed in the subsequent purification treatment. 4

Having selected the desired oil, the oxidizing operation consists in bubbling air therethrough, under proper conditions to obtainahigh acid num-' her and saponificationnumber andto avoid formation of large amounts of oil-insoluble products. For example, a highly solvent refined dewaxed Midcontinent type of parafiin base oil may be oxidized at 325 F. by blowing air therethroughuntil it shows an acid number of 8 and a saponification number greater than 8. Excessive oxidation is avoided and when that stage is approached where there is a tendency of further oxidation to produce oil-insoluble products the operation is terminated. These procedures in general do not particularly constitute any portion of the present invention, similar processes. for treatment oi somewhat similar materials being disclosed in various publications including the Burwell Patents Nos. 1,690,767; 1,690,768; 1,768,523; 1,863,004, James Reissue No. 18,522 and Sullivan No. 1,789,026 and literature citations therein. The oxidation of these materials may be conducted with the aid of catalysts in the form of metal" compounds as suggested by some of the patents or the oxidation may be catalyzed by inoculation with a portion of a previously oxidized batch of oil or paraffin. The oxidation may also be conducted at superatmospheric pressures. The reaction products from a normal oxidizing operation may contain 20% to 30% of oxidized material, a large proportion of which may be in the form of esters, anhydrides or lactones.

Sapomfication Having obtained the oxidized oils the desired acids will be separated according to any well known procedure, but a useful procedure is' to react the resultant materials with an alkaline compound such as calcium oxide or hydroxide under proper conditions of time and temperature to obtiin the formation of calcium soaps from the acidic and saponifiable compounds present in the reaction materials. These soaps are soluble in the oxidized oil and solid reaction products or residual products may be easily removed by filtering. If desired a small amount of bleaching clay may be added prior to, during or subsequent to the saponification operation. The filtered solution then represents a concentrated soap solution which can be diluted with the preferred lubricating oil to give a finished oil of the proper soap content.

Another useful procedure in obtaining the soaps from oxidation products is to saponify the entire oxidation products with aqueous alkali solution, separate unconverted hydrocarbon materials from the aqueous solution of alkali soaps of'synthetic petroleum acids, and then add calcium chloride solution which precipitates the calcium soaps'from the aqueous solution. The calcium soaps'are washed with hot water, and maybe dried as such or may be softened with a small amount of oil before dehydrating by heating. Again, this oil-soap concentrate is dilutable with oil.

In certain instances it is more convenient to separate the acidic. constituents from the other oxidation products in more or less pure form before converting into the oil-soluble soaps. A suitable method for this separation of the'synthetic petroleum acids from the oxidation products is now known to those skilled in the art (see Bur- Well) and is not a part of the present invention. Having separated the synthetic petroleum acids, which may also contain other oxygenated bodies according to the oxidation procedure and method of separation, I may now proceed in either of two ways: (1) I may dissolve or suspend the synthetic acids in warm sodium hydroxide solution to obtain a solution of sodium soaps, preferably avoiding a large excess of alkali. I next add calcium chloride, either solid or in aqueous solution, and precipitate the calcium soap which is washed and used as explained in the preceding paragraph; (2) I may dissolve the synthetic acids in lubricating oil, heating as necessary, and then react this acidified oil with lime (CaO or Ca(OH) 2) to give a soap solution in situ. This soap solution is heated to 325 F. to accomplish dehydration,

and filtered or centrifuged for the sake of clarification. The clarified soap solution is used directly or diluted with further quantities of oil depending'on the concentrationof soap.

Acid reaction products fines have been removedby dewaxing, as with propane; i. c. all materials having API gravity above 35 API. Such fractions have also had all naphthenic type lubricating oils removed by thorough solvent extraction 1. e., all oils lower than about 22 API. These oils thus have been fractionated to have an API range of 22 to 35, whereas undewaxed distillates have ranges of 5 to 50 API, and dewaxed distillates have ranges of 5 to 35 API and conventional acid treated distillates have ranges of 12 to 35 API. Materials of this type above 35 APT give acids whose calcium soaps are not as sufficiently oil-soluble or compatible as is often desired. The materials below 20 API give largely acids of sludge-like character which obviously are objectionable. Therefore materials ranging between 22 and 35 API constitute ideal oxidation stocks for the present purposes. Apparently it is only by drastic refining of high molecular weight fractions in the lubricating oil range, as above mentioned, that oxidation stocks may be obtained which yield acids and their soaps having high solubility in the lubricating oil. Soaps from SAE 10 or turbine oil grades enter into almost true solutions and are not removable in any incidental clay treatment. In using such oils it has been found possible to make a calcium soap concentrate by lime saponification of the entire body of the oxidized oil. In connection with the following table such an SAE 10 oil, as above mentioned, was oxidized to an acid number of 7.9 and to an estimated content of 20% of oxidation prod- Ash,

4 uctsQ 'I'hevarious columns of the table provide specifications of various materials and blends:

Tests on oxl- Tests on dized oil after limo saponification (4% i+ filter ay at 325 F.)

Tests on oxidized oil before lime saponification Tests on oil before oxidation saponlfied oxidized oil, in 90% naphthenic base oil' Gravity" Viscosity at 210 F. Viscosity gravity Baponification number Color, NPA

The addition of above 10% of oxidized paraffinic type oil, as above indicated, to a naphthenic base oil preferred as a base oil for Diesel engine lubricating purposes, yields in the product the desired 1% to 2% (about 1.35%) of soaps. How- 'ever, where the soaps are first segregated, they will be added in the indicated proportions.

In another instance, the oxidized oil shown above was treated with 4% calcium hypochlorite and a small amount of clay at elevated temperature, for the purpose of obtaining chlorination of the synthetic acids simultaneously'with soap formation. Analysis showed that approximately 7 1% chlorinewas taken up by the oxidized oil in this treatment.

In those cases where the oxidation stock will in itself constitute the proper lubricating. oil base, it will be within the range of the present invention to oxidize the entire oil lightly and then'to add lime or other calcium compounds to react with the oxidation products and produce directly Y in the oil the desired 1% to 2% of calcium soaps,

any residual or insoluble materials being removed a by filtering, the filtering taking place in conjunction with clayas above indicated if desired.

Water treatment I have discovered that lubricants, particularly lubricating oils made in accordance with this .invention, are sometimes rendered more stable to those uses where small quantities of water may be present, by boiling the lubricant after blending with'the soap with a small quantity of water for example 1% of water. As a result a proportion of the soap, perhaps A; to A, is precipitated out in an insoluble form and may be removed by filtering. For example, where the any given soap content in. the final product it is necessary to initially increase the soap forming materials correspondingly.

Addition agents In addition to the use of triethanolamine or "triethanolamine soap as hereinabove mentioned for the purpose of stabilizing and reduction of viscosity, I find it highly desirable for many purblend 4 lime 5 poses to incorporate otherv agents. As has been indicated above, especially the calcium soaps of various petroleum saponiflable oxidation products are of great value in the production of Diesel engine lubricating oils. These soaps serve primarily to prevent ring sticking; it is very likely that they possess a plasticizing, solubilizing or detergent action upon sooty, gummy, resinous and varnish-like materials which tend to form along rings and in piston grooves in high temperature service conditions. However, in addition to the anti-ring sticking function, it is especially desirable in heavy service lubricants of this type that other agents, other than the lubricating oil itself, be employed to impart what is often referred to by the indefinite termfoiliness. In the present instance the desired agent is one which reduces wear and overcomes tendencies toward scoring and seizing under overloads. Such materials impart to the lubricating oils definite increase in film strength. For example where the ordinary film strength of various lubricating oils extending from SAE 10 to SAE 60 grades are in the order of 5 to 10 pounds by the well-known Timken bearing fihn strength tests (see Industrial and Engineering Chemistry,

October 1936, pages1191 to 1197, see page 1196).

I have found that the film strength for satisfactory service in heavy Diesel engines of the high speed type under full load should be definitely above 16' pounds. For a description of the Timken testing machine and the method of test see SAE Journal, vol. 2851931, pages 53-60, an article by E. Wooler entitled Observations on testing lubricants. Various materials may be added-1o mineral lubricating oils which will bring the film strength range up. from the 5 to 10 pound range into the 25 to 50 pound range by the addition of only about 1% of material. The range of these additives will ordinarily be within about 0.5% to 4% or 5%. Such a highly desirable material is methyldichloro-stearate, other useful film strength improving agents are methyl-dichloro-palmitate, ethyl dichloro-margarate, methyl chloronaphthenate, chlorinated parafiin, chlorinated diphenyl oxide, and other chlorine containing compounds. Sulphur bearing compounds such as sulphurized sperm oil or sulphurized lard oil can also be used to impart the necessary film strengths to prevent seizing or scufllng of pistons, rings and cylinders.

The esters of chlorinated synthetic petroleum acids, such as the methyl or ethyl esters of chlorinated synthetic petroleum acids produced from parafiinic wax or from paraflinic oil, are particularly valuable oiliness and film strength addition agents. In "'chlorinating the synthetic petroleum acids, a chlorine content of 20% to 30% is found satisfactory and is easily obtained by direct chlorination of the acids by bubbling chlorine therethrough after they have been separated from the oxidation products. Esterification is easily accomplished by well known methods. I

When I chlorinate the synthetic petroleum acids and then employ these acids for the production of the soap used in compounding the lubricating oil, sufilcient film strength and adequate stability in the compounded oil are usually obtained without the use of other addition agents. In fact, the soaps of the chlorinated synthetic acids show such marked improvement in both film strength imparting property and in solubility in mineral oil that the step of chlorinating the synthetic petroleum acids represents a valuable advance in the production of Diesel engine lubricants.

My invention therefore also includes the addition of chlorinated or sulphurized or other oiliness or film strength agents to overcome seizing and scum'ng as above described, either as separate addition agents or contained in the soap.

employed.

These various soaps preferably are calcium soaps, for most purposes, but magnesium and other metal soaps mentioned may be used where suitable and suiliciently oil-soluble. Also aluminum soaps may be used where suitable and suiiiciently oil-soluble, bothas to the chlorinated and unchlorinated synthetic materials. This applies also when employing oiliness or anti-wear addition agent, and the same is true when triethanolamine or its soaps areadded for the purpose of stabilizing and controlling viscosity.

It is to be understood that these disclosures are given as merely illustrative of the generic invention.

Iclaim:

1. A. method for producing lubricants comprising oxidizing a highly reflned'paramnic type lubricating oil to producein the oil reaction products including petroleum acids, adding a calcium compound to the resultant mixture to react with the saponiflable materials, filtering, and adding the resultant soap-oil solution to a naphthenic type lubricating oil to yield between about 0.8% and 3% of total soap in the resultant lubricating oil composition.

2. A Diesel engine lubricating oil comprising a naphthenic base lubricating oil containing a troleum acids produced by the oxidation of pe troleum lubricating oil fractions, adding a small quantity of water in the order of 1% to 2% to the oil, boiling the mixture and thereby precipitating insolubles formed under such conditions,

' filtering, and recovering the oil.

4. A wax-iree mineral lubricating oil containing a snail quantity, in the order of 1% to 2% ofan alkaline earth metal soap of acids obtained by the oxidation of highly refined solventextracted petroleum lubricating fractions.

5. A wax-flee mineral lubricating oil {or Diesel engines containing between about 0.6% and 3% or an oil-soluble metal soap of'petroleum acids obtained by oxidation of highly paraflinic heavily solvent-extracted petroleum lubricating oils, the proportion of soap being sumcient to control the deposition of resinous and varnish-like materials in the engine but insumclent to increase substantially the viscosity of the original lubricating oil. 6. A Diesel engine lubricating oil comprising a naphthenic base lubricating oil containing a small quantity within the range of 0.8% to about 3% of a calcium soap of petroleum acids obtained by oxidation of petroleum lubricating oil fractions of highly paramnic nature.

7. A Diesel engine lubricating oil comprisinga tion of highly paramnic heavily refined, solvent lubricating oil containing a small quantity in the range of about 0.8% to about 3% of oilsoluble lubricating oil produced by heavily treating the dewaxed oil with selective solvents capable of removing the aromatic and other unprotected non-paraflinic materials, said soap entering into almost complete true solution in the lubricating oil.

8. An oil according to claim 7 wherein the oil- -soluble metal soap is calcium soap.

9. A Diesel engine lubricating oil comprising -a naphthenic mineral lubricating oil containing between about 0.8% and 3% of an oil-soluble metal soap of petroleum acids produced by the oxidation of para'ifinic petroleum lubricating distillates.

10. A lubricant comprising a mineral lubricating oil containing a quantity of calcium soap of petroleum acids obtained by the oxidation of heavily solvent-treated petroleum lubricating fractions having a gravity between 22 and A. P. I. at F. 1

11. A liquid lubricant comprising a miner lubricating oil containing a quantity of calcium soap ofpetroleum acids obtained by the oxidatreated dewaxed mineral lubricating oils.

12. An 011 according to claim 2 wherein the soaps are produced from chlorinated petroleum acids.

13. An oil according to claim 9 wherein the soap contains chlorine.

14. A lubricant according to claim-11 wherein the soap contains chlorine.

15. A lubricating oil for severe service internal combustion engines comprising a naphthenic base mineral lubricating oil containing ancilsoluble soap of petroleum synthetic acids ch- *tained by the omdation of highly paraflinic petroleum fractions, said soap being present in :quantities suflicient to overcome the deposit of gummy, resinous andvarnish-like materials about the rings of severe service internal combustion engines but insufficient in quantity to impart grease-like characteristics to the oil and substantially increase the viscosity of the original oil. 4

16. A Diesel engine oil comprising a lubricating oil containing a small quantity of an oil-soluble metal soap of synthetic acids obtained from the emulation ot-highly paramnicmineral oil which is substantially free from fractions soluble in sulfur diomde-benzene mixtures, furfural, di- "chloroethylether, phenol, cresohand nitro-ben- -zene, said soap entering into substantially complete solution in the lubricating oil. f

17. A lubricating oil comprising a small quantity between about 0.5% and about 2% of an oilsoluble soap of synthetic petroleum acids pro- .duced by the omdation of highly refined pars ammo-type petroleum lubricating oil fractions to "yield a freely liquid lubricating oil tree from substantial increase in viscosity over that ofv the base oil.

' 18. A lubricating oil according W (#181111 f wherein the soap is a calcium soap.

nrnrc B. 

